It is often the case that the driver of a vehicle wants to follow a vehicle in front. Perhaps only the driver of the vehicle in front knows the way to a desired location. That driver needs to be aware of the presence of the vehicle behind, and to pull over, speed up or slow down, depending on the progress of the follower vehicle. Likewise, the person driving the follower vehicle needs to be aware at all times of the location of the vehicle they are following. Indeed, more so, because, should the followed vehicle turn off the road unexpectedly, it is easy for the following driver to miss this and to end up driving past and the vehicles becoming separated. The problem occurs because the driver of the follower vehicle, particularly in heavy traffic, often has too many things to think about and to handle, and may have to suspend concentration on following the vehicle in front to deal with more important issues. Other occasions also require one vehicle to follow another. Sometimes, it is desired simply to “go in convoy”, whether both drivers know the route or not. However, on such journeys it is sometimes not known when one vehicle stops, for refuelling or because of some problem, or simply which vehicle is in front. This is a particular issue during heavy traffic on long journeys. At other times, perhaps police vehicles need to follow a suspicious car.
There are other cases where it might be desirable to follow the precise course of another vehicle. One example is in off-road driving where a lead vehicle might have an experienced driver or one who knows the terrain and follower vehicles should follow substantially exactly the same route. Indeed, whether off-road or otherwise, there may be circumstances where control of a vehicle might best be handled by a system capable of following another vehicle. It would certainly be desirable for a vehicle to have a system capable of following another vehicle or even a person, such as a cyclist, or at the least to be able to navigate to a location not necessarily known to the driver of the vehicle.
US-A-2006/0221328 discloses homing systems applicable to pairs of objects (such as, e.g., ground vehicles, watercraft, aircraft, spacecraft, etc.) wherein one or both of the objects are moving (such as moving in two-dimensions or three-dimensions) and one or both of the objects may be unmanned. When paired objects are disposed in line of sight (LOS) of each other, with one object having disposed thereon an automatic frequency emitter emitting at least two frequencies (preferably at least two frequencies wherein the frequencies are in a range of light, most preferably, laser light), the other object may automatically follow that object having the emitter disposed thereon, with the following being accomplished by using an automatic detector that detects the emitted frequencies, with the detecting and following operations most preferably accomplished completely without needing a human operator. The need for human operators may be eliminated in certain contexts, such as dangerous operations. Such a system requires both vehicles to be adapted for the task of one following the other.
Japanese Patent Publication No. 60-33352 discloses a method of following an image of a preceding vehicle as sensed by an image sensor such as a video camera. According to this method, the driver of a vehicle needs to manually set and continuously adjust an image-following gate or window enclosing an object to be followed on a display screen while looking at the screen, so as not to lose sight of the image of the preceding vehicle.
U.S. Pat. No. 5,304,980 discloses distance detecting apparatus for a vehicle which, once the driver sets an image-following window enclosing a target preceding vehicle, is able to measure the distance to the target preceding vehicle in an automatic fashion, without the need of any movement of the apparatus, provided that the preceding vehicle lies in the field of view of the apparatus. The distance detecting apparatus comprises a pair of optical sensing means each for optically sensing a plurality of objects and generating a corresponding image signal; first memory means for storing the output image signal from one of the optical sensing means as a first image signal; second memory means for storing the output image signal from the other of the optical sensing means as a second image signal; a display with a screen for displaying the images of the objects as sensed by the optical sensing means; window setting means for successively setting an image-following window on the screen of the display at a location enclosing a target preceding vehicle as well as a plurality of distance-measuring windows at predetermined locations on the screen of the display; distance calculating means for comparing the images of the objects in the respective windows stored in the first memory with the corresponding images of the objects stored in the second memory so as to detect deviations therebetween, the distance calculating means individually calculating the distance to an object in each window based on the calculated deviations; and image-following-window updating means for successively comparing at predetermined intervals an image in the image-following window, which is currently sensed by one of the optical sensing means and stored in the first memory, with an image of the target vehicle, which was previously sensed by the one of the optical sensing means and stored in the first memory, so as to update the image-following window at a location which provides the best match therebetween. However, the use made of the apparatus is not explained.
Some modern vehicles are provided with front-facing cameras for the purpose of emergency braking in the event that a driver is not paying attention, or in any event when a collision appears inevitable. Braking in this event is to mitigate the effects of a collision rather than prevent a collision. By the time an automatic system has calculated that it is too late for a driver of the vehicle to avoid a collision by voluntary means, it is also too late for the automatic system to avoid. However, while it remains feasible for the driver to avoid a collision, the current course and speed of the vehicle may be for good reason and it is not acceptable for an automatic system to override the control of a human driver in this circumstance. However, once a collision becomes inevitable, the vehicle can automatically attempt to mitigate the effects of the collision, by applying the brakes, based on the presumption that this is in the best interests of all concerned. In order to avoid a collision, some systems at least warn the driver, by some means, when a collision appears likely. Such systems rely on forward facing object sensing means that measure the distance to objects in front, for example, using radar or, indeed, video cameras. Video cameras, or at least computers supplied with their image data, now have sophisticated image recognition capabilities that enable them to detect that an object is in the field of view, its distance from the camera and its relative speed in relation to the camera. The image processing of such cameras can be very sophisticated and, hence, expensive. Less expensive cameras are sometimes employed to recognise road signs and to warn drivers, for example, when they are exceeding a speed limit, or approaching a bend. They are less sophisticated since the task of recognising what a road sign says is relatively trivial compared with distinguishing objects in the path of a vehicle.
Some vehicles are provided with satellite navigation equipment. Satellite navigation equipment (“SatNav”) is based on a GPS (global position sensing) system that triangulates a vehicle's position, and the direction in which it is facing, from signals received from several satellites. Implicit in such a system is an accurate map of the region in which the vehicle is driven. Most SatNavs integrate the position sensing system with the map to correlate position and direction sensed by the system with likely position and direction on the map. Ultimately, if the SatNav's calculation of position (based on speed and anticipated direction on a road of the map, for example following a pre-programmed route), departs too far from the GPS-sensed position and direction, then the GPS-sensed position and direction takes precedence and the system assumes that the vehicle is deviating from the road, possibly following an alternative (perhaps unmarked) road, or going off-road.
It is an aim of the present invention to provide a convenient system enabling a preceding vehicle to be followed.